Leucine aminopeptidase isolated from bovine lens tissue is the subject of a number of investigations designed to elucidate the mechanism of catalysis and its possible role in the development of cataracts. The effect of variation in the length of peptide chain on the kinetic parameters for the release of the N-terminal amino acid will be measured in order to map the substrate binding site. The effect of substitution of zinc by other metal ions (Ni2 ion, Co2 ion, and Cd2 ion) on the properties of the enzyme will be determined in order to obtain information on the metal ligands. A number of putative "active-site" directed inhibitors will be prepared in an attempt to identify the functional groups at the catalytic center. An investigation of the 3-dimensional structure by X-ray diffraction will be undertaken.